[Ocfs2-devel] [PATCH] ocfs2: fix double unlock in case retry after free truncate log

[Joseph Qi <joseph.qi@huawei.com>]

Hi Eric,

On 2016/9/14 15:57, Eric Ren wrote:
> Hello Joseph,
> 
> Thanks for fixing up this.
> 
> On 09/14/2016 12:15 PM, Joseph Qi wrote:
>> If ocfs2_reserve_cluster_bitmap_bits fails with ENOSPC, it will try to
>> free truncate log and then retry. Since ocfs2_try_to_free_truncate_log
>> will lock/unlock global bitmap inode, we have to unlock it before
>> calling this function. But when retry reserve and it fails with no
> You mean the retry succeeds by "retry reserve", right? I fail to understand in which situation
> the retry will fail to get global bitmap inode lock. Because I didn't see this problem when I
> tested my patch, could you explain a bit more?
> 
> Eric
Before retry it has inode unlocked, but ac inode is still valid. And
if inode lock fails this time, it will goto bail and do inode unlock
again.

Thanks,
Joseph

>> global bitmap inode lock taken, it will unlock again in error handling
>> branch and BUG.
>> This issue also exists if no need retry and then ocfs2_inode_lock fails.
>> So fix it.
>>
>> Fixes: 2070ad1aebff ("ocfs2: retry on ENOSPC if sufficient space in
>> truncate log"
>> Signed-off-by: Jospeh Qi <joseph.qi@huawei.com>
>> Signed-off-by: Jiufei Xue <xuejiufei@huawei.com>
>> ---
>>   fs/ocfs2/suballoc.c | 13 +++++++++++--
>>   1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
>> index ea47120..041453b 100644
>> --- a/fs/ocfs2/suballoc.c
>> +++ b/fs/ocfs2/suballoc.c
>> @@ -1199,14 +1199,23 @@ retry:
>>               inode_unlock((*ac)->ac_inode);
>>
>>               ret = ocfs2_try_to_free_truncate_log(osb, bits_wanted);
>> -            if (ret == 1)
>> +            if (ret == 1) {
>> +                iput((*ac)->ac_inode);
>> +                (*ac)->ac_inode = NULL;
>>                   goto retry;
>> +            }
>>
>>               if (ret < 0)
>>                   mlog_errno(ret);
>>
>>               inode_lock((*ac)->ac_inode);
>> -            ocfs2_inode_lock((*ac)->ac_inode, NULL, 1);
>> +            status = ocfs2_inode_lock((*ac)->ac_inode, NULL, 1);
>> +            if (status < 0) {
>> +                inode_unlock((*ac)->ac_inode);
>> +                iput((*ac)->ac_inode);
>> +                (*ac)->ac_inode = NULL;
>> +                goto bail;
>> +            }
>>           }
>>           if (status < 0) {
>>               if (status != -ENOSPC)
> 
> 
> 
> .
>